1. Field of the Invention
The present invention relates to raw material feeding devices for injection molding machine, and, more particularly, to a mounting structure for a granulate hopper on the plastification cylinder of an injection unit which is selectively convertible for use with a horizontally oriented injection unit or a vertically oriented injection unit.
2. Description of the Prior Art
A prior art structure, designed to accomplish convertibility of the hopper arrangement for horizontal and vertical orientation of the injection unit is disclosed in German Pat. No. 11 50 192. There, the axis of the flow channel which leads from the hopper base into the plastification cylinder is arranged at an acute angle with respect to the longitudinal axis of the injection unit. The hopper itself has a base portion which is axially aligned with the flow channel and is rotatable about the axis of that channel. However, the shape of the hopper is asymmetrical with respect to its axis of rotation, so that a major portion of its outline and interior cavity is located on one side of the axis of rotation. Because the axis of rotation of the hopper forms an angle of 45.degree. with respect to the injection unit axis, and because the crown portion of the hopper is likewise inclined by 45.degree. against the flow channel axis, it is possible to selectively orient the crown portion of the hopper in either a perpendicular or a parallel orientation with respect to the injection unit, through rotation of its base attachment by 180.degree..
A major shortcoming of this prior art solution is related to the fact that the flow channel which links the hopper base portion to the plastification cylinder is inclined at 45.degree.. This inclination may lead to flow problems, especially for poorly flowable raw materials, such as pulverulent plastic raw materials, for example, for which a vertical flow channel may be desirable or even necessary.